A six-foot length of safety fuse will burn for how many minutes?

• A. 2 minutes
• B. 6 minutes
• C. 8 minutes
• D. 4 minutes

Answer: (D)

A fuse’s burn time is determined by a constant burn rate: the length that burns grows at a steady pace over time, so longer pieces take more time to burn.

For a six-foot piece, using a typical steady burn rate of about one and a half feet per minute, the calculation is straightforward: six feet divided by 1.5 feet per minute equals roughly four minutes. That’s why the six-foot fuse is expected to burn for about four minutes.

If you imagine other durations, they would require unrealistically different burn rates for the same fuse length—three feet per minute would shorten it to about two minutes, one foot per minute would stretch it to six minutes, and three-quarters of a foot per minute would push it to about eight minutes. The four-minute duration fits the common, steady-burn behavior of safety fuses.